How long should I cook Tilapia fillets? I marinated them and want to cook them in the marinade to really?

flavor them-I hate fish so I am trying to get rid of a lot of the fishy taste with lemon pepper marinade. I have never cooked fish before because I don't like it but my husband does so I don't want to screw it up. How do you know when it's done and cooking it at 400 degrees, how long do I cook it for?